1. Field of the Invention
The present invention relates to a deterioration diagnosis system to diagnose bearing deterioration, insulation deterioration and the like in a rotational machine such as a motor and a generator.
2. Description of the Related Art
A rotational machine such as a motor and a generator may stop due to a sudden failure, which may cause heavy losses. Especially in the case of a shutdown resulting from a sudden failure of a high-voltage motor used in plant equipment or in a similar facility could cause a significant adverse impact such as a reduction in production capacity utilization and a revision of production plans. Survey results show that about 40% and 25% of high-voltage motor failures are caused by deterioration of a bearing and of stator winding insulation, respectively. In addition, variable-speed drive/an inverter is becoming commonly applied in a high-voltage motor for the purpose of energy saving, which leads to a problem of accelerations in insulation deterioration due to an inverter surge and in bearing deterioration due to electric erosion. This trend is anticipated to be more conspicuous because of the appearance of semiconductor devices using a new material such as silicon carbide (SiC). Therefore, there is an increasing demand to achieve a highly accurate diagnosis of bearing deterioration and insulation deterioration during operation, to prevent a sudden failure of a motor and a generator.
To meet such demand, JP-06-138168-A, for example, discloses a technique for measuring automatically, in an operating state, a maximum discharge magnitude of a partial discharge which occurs during operation, by means of a current sensor attached to a feeder. In addition, JP-2013-130440-A discloses a technique for calculating an insulation resistance of each phase, by means of a harmonic of a measured zero-phase current. Further, JP-2007-288829-A discloses a technique for detecting an abnormality of a machine connected to a motor by comparing actually-measured frequency and current with preset abnormal values of frequency and current, respectively.